Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
  • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/021—Physical characteristics, e.g. porosity, surface area
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated
  • Y10T428/2998—Coated including synthetic resin or polymer

Definitions

• a lithium ion secondary battery includes a positive electrode capable of inserting and extracting lithium ions, a negative electrode, and an electrolytic solution containing a non-aqueous electrolyte.
• a positive electrode capable of inserting and extracting lithium ions
• a negative electrode for the negative electrode material, artificial graphite obtained by shaping mesophase small spheres / coke from a low-crystalline carbon material such as resin charcoal, or a material having a high degree of graphitization such as natural graphite is used. Further, a material having a high degree of graphitization that satisfies the demand for a high energy density is desired.
• the discharge capacity is close to the theoretical value for materials that have been graphitized, including natural graphite.
• the irreversible capacity associated with the decomposition of the electrolytic solution on the negative electrode in the initial stage of charging is generally as large as several tens mAh Z g or more. Therefore, this has been a major obstacle in improving the performance of the lithium ion secondary battery.
• propylene carbonate is used for the electrolyte, significant decomposition of the electrolyte occurs on the negative electrode. As a result, propylene carbonate Has been greatly limited in use as an electrolyte.
• JP-A-4-370662 and JP-A-5-335016 disclose, as a negative electrode material, the surface of the black sharp particles with an organic carbonized material. Coated materials are disclosed. Further, a method of coating a carbonaceous powder with a carbonized powder of petroleum pitch or coal tar pitch is disclosed in JP-A-10-59703. Also, a material in which the surface of graphite particles is coated as a carbon layer by a chemical vapor deposition method is disclosed in Japanese Patent Application Laid-Open No. 11-204109.
• the present invention can achieve high efficiency without lowering the reversible capacity, reduce irreversible capacity, remarkably decompose the electrolytic solution at the beginning of charging, and restrict the use of propylene carbonate.
• An object of the present invention is to provide a negative electrode material for a lithium ion secondary battery that can be used even in a system electrolyte. Disclosure of the invention
• the irreversible capacity accompanying the decomposition of the electrolyte can be reduced. If the amount of mesopores is larger than 0.01 c cZg, the irreversible capacity is not improved.
• Peak intensity ratio of 1360 cm- 1 to 1580 cm- 1 in Raman spectrum analysis at a wavelength of 532 nm, R I 1360 / I 158 . However, since it is 0.4 or less, preferably 0.37 or less, and more preferably 0.35 or less, the irreversible capacity can be reduced.
• the coated graphite powder has an acid consumption rate of 2 wt% or more when oxidized for 1 hour in an atmosphere of 400 ° C. and an air flow rate of 31 min. Is preferred.
• the irreversible capacity can be greatly reduced, and the resistance to propylene carbonate can be improved.
• the coated graphite powder has a BET specific surface area of 0.5 to 4 m 2 Zg using a nitrogen atom as an adsorbate.
• a preferable range of the specific surface area is 0.5 to 4 m 2 / g, more preferably 0.5 to 3 m 2 / "g.
• the coated graphite powder has an HZC value of 0.01 or less in elemental analysis.
• H represents a hydrogen atom
• C represents a carbon atom
• the HZC value represents the HZC atomic ratio in the entire carbonaceous material contained in the multiphase structure including the surface layer and the nucleus. Is given as the average of
• a mixture of two types of graphite powders having different average particle diameters each having an average particle diameter of 10 to 50 m and a standard deviation ratio (crZD) to the average particle diameter of 0.02 or less.
• the average particle size is as small as 8 jiim to 15 / m, more preferably 10 ⁇ m to 13; xm, and as large as 15 ⁇ ! 25 ⁇ , more preferably 18 ⁇ to 22 m.
• the graphite powder has an average plane distance d using a Gakushin method. . 2 value is 0. 3380 nm or less and a L (1 12) is 5 nm or more.
• the binary value is preferably 0.3380 nm or less, and L (1 12) is preferably 5 nm or more.
• the good preferable range, (1.02 value 0. 3370 nm or less, L (1 1 2) is preferably not less than 10 nm, more preferably, £ 1. 02 value 0. 3360 nm or less, L ( 1 1 2) is 15 nm or more.
• the coating of the carbonized thermoplastic resin causes the surface of the coated graphite powder to have a larger amount of pores or inter-particle voids than the mesopores while decreasing the amount of the mesopores. Increasing the amount of pores larger than the mesopores makes it easier for the electrolyte to penetrate into the particles. On the other hand, since the amount of mesopores is reduced, the irreversible capacity associated with the decomposition of the electrolyte can be reduced. That is, it can be said that the coating in the present invention is not the particle surface but the coating inside the pores. Further, in the negative electrode material for a lithium ion secondary battery of the present invention, the coated graphite powder has a carbonization yield of 20 wt. % Or less of carbonized thermoplastic resin is preferably coated at a ratio of 100 parts by weight or less to 100 parts by weight of the black bell powder.
• thermoplastic resin is any one of polychlorinated vinyl, polyvinyl alcohol, and polyvinylpyrrolidone, or a mixture thereof.
• the particle shape is not particularly limited, but a spherical shape is preferable from the viewpoint of coating properties on a copper plate and lithium ion diffusibility. Natural graphite and the like are often in the form of flakes.
• a particle complexing device such as a hybridization system manufactured by Nara Machinery Co., Ltd. or a mechanofusion system manufactured by Hosokawa Micron Corporation is used. Can be spherical.
• the mixing of the graphite powder and the thermoplastic resin may be performed in a dry manner using a known mixing device such as a V-type mixer. Uniform mixing is preferred, but a pole mill or hammer mill can be used as long as the graphite particles are not destroyed by shearing force. It is also possible to use a device such as a file.
• a known mixing device such as a V-type mixer. Uniform mixing is preferred, but a pole mill or hammer mill can be used as long as the graphite particles are not destroyed by shearing force. It is also possible to use a device such as a file.
• the firing of the mixture is usually performed in an atmosphere of an inert gas such as nitrogen or argon.
• the firing temperature may be a temperature at which carbonization is completed, but is usually 700 ° C or higher, preferably 750 ° C or higher, preferably 1100 ° C or lower, more preferably 1000 ° C or lower, and particularly preferably. Is below 950 ° C. If the temperature is too low, carbonization is insufficient and sufficient performance as an electrode active material cannot be obtained.If the temperature is too high, the crystallinity is so high that the electrolyte can be easily decomposed and the irreversible capacity decreases. Not preferred for purpose.
• the heating rate is not particularly limited, but ⁇ ⁇ ⁇ ⁇ Preferably from 20 : L 00 ° C / h.
• V 1 2 is when the relative pressure is changed from X to X 2 ( ⁇ ,
• ⁇ X 2 increase in the amount of adsorption
• r ⁇ is the average value of the pore radius to be determined
• ⁇ 1: is the change in the thickness of the molecular adsorption layer
• r is the average value of the pore radius
• VJ 2 is the pore radius r ⁇ From! ⁇
• C x is a variable (chosen from 0.75, 0.80, 0.85, 0.90)
• S is the pore surface area.
• the obtained coated black powder coated with the carbonized thermoplastic resin does not undergo a crushing step after firing, and after a particle size adjustment by simple sieving, using a binder and a solvent capable of dissolving the binder. Dispersed paint can be used.
• the binder it is necessary to be stable with respect to the electrolytic solution and the like, and various materials are used from the viewpoints of weather resistance, chemical resistance, heat resistance, flame retardancy, and the like.
• inorganic compounds such as silicate and glass, alkane polymers such as polyethylene, polypropylene, poly (1,1-dimethylethylene), unsaturated polymers such as polybutadiene and polyisoprene, polystyrene, and poly Examples thereof include polymers having a ring structure in a polymer chain, such as methylstyrene, volibulpyridine, and poly-N-vininolepyrrolidone.
• binder examples include acryl derivative polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, and the like, and polyolefin.
• Fluorinated resins such as vinyl chloride, polyvinylidene fluoride, and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol; polyvinyl chloride; and polyvinyl chloride Halogen-containing polymers such as viurydene, polyanily
• a conductive polymer such as a polymer can be used.
• binders include a fluororesin and a CN group-containing polymer, and more preferably polyvinylidene fluoride.
• the amount of the binder used is usually at least 0.1 part by weight, preferably at least 1 part by weight, and usually at most 30 parts by weight based on 100 parts by weight of the coated graphite powder coated with the carbonized thermoplastic resin. And preferably not more than 20 parts by weight. If the amount of the binder is too small, the strength of the electrode tends to decrease, and if the amount of the binder is too large, the ion conductivity tends to decrease.
• a solvent that can dissolve the binder to be used may be appropriately selected, and examples thereof include N-methylpyrrolidone and dimethylformamide, and N-methylpyrrolidone is preferable.
• Example 1 Mean spacing d by Gakushin method. . 2 is 0.353 54 nm, L (1 1 2) showing the three-dimensional size of crystallites is 27 nm, average particle diameter 20 ⁇ m
• Natural graphite powder 100 parts by weight of polybutyl alcohol powder 50 The parts by weight were dry-mixed at room temperature for 10 minutes using a mixer. The mixed graphite powder is transferred to a graphite crucible, covered, heated in a nitrogen stream to 900 ° C at 300 ° C / h, held at 900 ° C for 1 hour, and cooled. did.
• Example 2 The same formulation as in Example 1 was used except that the blending amount of the polyvinyl alcohol powder was 75 parts by weight, the standard deviation ratio ( ⁇ / D) to the average particle diameter of 24 ⁇ m ( ⁇ / D) was 0.0085, and the mesopore volume was 0.005. [0060] A coated black bell powder coated with a carbonized material of cc / g was obtained. Using this, the same electrochemical measurement as in Example 1 was performed.
• Example 1 Electrochemical measurement was performed in the same manner as in the above.
• Mean spacing d by Gakushin method. . 2 is 0.3354 nm
• L (1 1 2) showing the three-dimensional size of crystallites is 27 nm
• 50 parts by weight of natural graphite powder with an average particle diameter of 12 ⁇ m is the average plane distance by the Gakushin method d. . 2
• L (1 1 2), which indicates the three-dimensional size of crystallites was 27 nm
• a mixed powder of 50 parts by weight of natural graphite powder with an average particle diameter of 24 ⁇ m was used.
• Example 2 It was coated with a carbonized material having a standard deviation ratio ( ⁇ / D) of 0.011 and a mesopore volume of 0.0083 cc / g with the same formulation as in Example 1 except for the average particle diameter of 19 ⁇ m. A coated graphite powder was obtained. Using this, the same electrochemical measurement as in Example 1 was performed.
• Mean spacing d by Gakushin method. . 2 is 0.3355 ⁇
• L (1 1 2) indicating the three-dimensional size of crystallites is 27 nni
• average particle diameter is 19, and 100 parts by weight of natural graphite powder is subjected to the same treatment as in Example 1;
• the standard deviation ratio ( ⁇ / D) for a particle size of 23 m is 0.008, and the mesopore volume is 0.0
• a coated graphite powder coated with a carbonized material of 055 cc / g was obtained. Using this, the same electrochemical measurement as in Example 1 was performed.
• the battery was charged and discharged at a current density of 3.12 mA cm- 2 .
• the ambient temperature was 25 ° C
• a discharge capacity of 363.6 mAhZg was obtained.
• the ambient temperature was 15 ° C.
• it was 311.2 mAh Zg
• the capacity retention ratio at 25 ° C. was 85.6%.
• Example 1 Except that the blending amount of the polyvinyl alcohol powder was changed to 10 parts by weight, the ratio ( ⁇ / D) of the standard deviation to the average particle diameter of 24 / xm ( ⁇ / D) was 0.018, and the mesopore volume was 0.018, with the same formulation as in Example 1. A coated graphite powder coated with a cc / g of carbonized material was obtained. Using this, the same electrochemical measurement as in Example 1 was performed.
• Example 1 Except that the blending amount of the polyvinyl alcohol powder was 200 parts by weight, the ratio of the standard deviation to the average particle diameter of 24 ⁇ (and ZD) was 0.007, and the mesopore volume was 0.0055 cc, with the same formulation as in Example 1. / g, and a coated graphite powder coated with a carbonized material having an R value of 0.51 was obtained. Using this, the same electrochemical measurement as in Example 1 was performed.
• Example 2 Except that the heat treatment after dry mixing was performed at 600 ° C lower than that of Example 1, the standard deviation ratio ( ⁇ / D) to the average particle diameter of 24 ⁇ m ( ⁇ / D) was 0.012, A coated graphite powder coated with a carbide having a pore volume of 0.0050 cc / g, an R value of 0.47, and an HZC of 0.02 was prepared. Obtained. Using this, the same electrochemical measurement as in Example 1 was performed.
• Example 2 Except that the heat treatment after dry mixing was performed at 1300 ° C higher than that of Example 1, the standard deviation ratio ( ⁇ / D) to the average particle diameter of 24 ⁇ m ( ⁇ / D) was 0.012 with the same formulation as in Example 1. Coated with carbonaceous material having a mesopore volume of 0.0063 cc / g and oxidation consumption of 0.13 wt% when oxidized for 1 hour in an atmosphere of 400 ° C and an air flow rate of 31 / min. A coated black powder was obtained. Using this, the same electric physics measurement as in Example 1 was performed.
• Der 1 mu m by Gakushin method Except that natural graphite powder was used, the same formula as in Example 1 was used to obtain a standard deviation ratio ( ⁇ / D) of 0.032 to an average particle size of 8.2 ⁇ and a mesopore volume of 0.0202 cc / g.
• a coated graphite powder coated with a carbide was obtained, and the same electrochemical measurement as in Example 1 was performed.
• the natural graphite powder used in Example 1 was used without being coated with a carbonized material, and the graphite powder was used as a solvent with N-methinolepyrrolidone so that the amount of a binder composed of polyvinylidene fluoride resin was 1% by weight.
• the slurry was adjusted. After applying this slurry to the copper foil, the solvent is sufficiently volatilized and pressed using a roll press so that the approximate density becomes 1.0 g / cm 3. This was extended to obtain a negative electrode. Using this negative electrode, a three-electrode cell was produced. Counter,.
• Fig. 1 shows a list of various measurement data.
• the negative electrode material for a lithium ion secondary battery according to the present invention is configured as described above, and can achieve high efficiency without lowering the reversible capacity.
• the use of propylene carbonate-based electrolytes, in which the decomposition of the electrolyte is remarkable and its use is restricted, can be used.

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